QD 


$B    35    3M1 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA, 

RECEIVED    BY    EXCHANGE 


Class 


The  Use  of  the  Rotating  Anode 

in 
Electrolytic  Separations 


THESIS 

Presented  to  the  Faculty  of  the  Department  of  Philosophy 

of  the 

University    of  Pennsylvania 
in  Partial  Fulfilment  of  the  Requirements 

for  the  Degree  of 
Doctor  of  Philosophy, 


BY 

MARY   ELISABETH  HOLMES 

MYSTIC,  CONN. 

1908 


HODGES  &  KIRK 

PHII,  ADEI^PH  I A 
1908 


UNfVER 
x  •<•>      OF 

fe/EPRWVJ 


The  Use  of  the  Rotating  Anode 

in 
Electrolytic  Separations 


THESIS 

Presented  to  the  Faculty  of  the  Department  of  Philosophy 

of  the 

University   of  Pennsylvania 
in  Partial  Fulfilment  of  the  Requirements 

for  the  Degree  of 
Doctor  of  Philosophy, 

BY 

MARY   ELISABETH  HOLMES 

MYSTIC,  CONN. 
1908 


HODGES  &  KIRK 

PHILADELPHIA 
1908 


ACKNOWLEDGMENT. 

This  work  was  undertaken  at  the  suggestion  of  Dr.  Edgar  F. 
Smith,  and  the  writer  wishes  to  express  sincere  appreciation 
of  his  helpfulness  and  friendliness,  not  only  in  this,  but  in  all 
the  work  of  the  past  two  years. 


OF  THE 

{    UNIVERSITY  ) 

OF 


INTRODUCTION. 

This  investigation  was  undertaken  for  the  purpose  of  prov- 
ing whether  satisfactory  separations  of  metals  could  be  made 
with  the  rotating  anode,  using  low  currents.  Many  separations 
with  stationary  electrodes  have  been  made  with  low  currents, 
but  with  the  rotating  anode,  high  currents  of  from  three  to  five 
amperes  have  been  employed.  The  largest  contribution  to  the 
subject  of  metal  separations,  using  the  rotating  anode,  was  made 
by  Ashbrook  in  1904  (Journal  of  the  American  Chemical  So- 
ciety, 26,  1285).  All  his  work  was  done  with  high  currents, 
five  amperes  being  generally  used.  A  few  separations  were 
later  recorded  by  Miss  Langness  (Thesis,  1906),  in  which  low 
currents  and  rotation  were  successful.  Silver  was  separated 
from  copper,  nickel,  platinum  or  zinc,  using  the  cyanide  elec- 
trolyte, the  current  ranging  from  0.25  to  0.4  amperes.  The 
analysis  of  a  coin,  as  performed  by  Miss  Langness,  was  made 
possible  by  the  fact  that  silver  could  be  deposited  completely 
by  such  a  low  current  as  0.4  ampere,  while  the  copper  required 
a  much  higher  current.  The  time  given  to  these  silver  separa- 
tions was  about  twenty  minutes.  These  results  would  seem  to 
indicate  the  possibility  of  obtaining  other  separations  with  low 
currents  in  comparatively  short  periods  of  time. 

Criticism  of  the  rapid  methods  of  electrolytic  work  has  often 
been  made  to  the  effect  that  while  the  methods  employed  may 
be  adequate  for  the  determination  of  single  metals,  the  intro- 
duction of  more  than  one  metal  into  the  solution  causes  such 
a  variation  in  conditions  that  separations  are  not  practicable. 
The  only  answer  to  such  doubts  is  a  systematic  study  of  the 
whole  subject  of  separations,  varying  conditions  of  current,  ro- 
tation, time  and  electrolyte  used,  so  that  for  each  metal  all  pos- 
sibilities may  be  determined.  Through  the  following  work,  a 
beginning  of  such  study  has  been  made  with  the  element  cad- 
mium. The  possibilities  of  its  separation  at  low  currents  from 
the  metals  of  Groups  III  and  IV,  and  from  magnesium,  have 


186933 


been  ascertained,  and  a  comparison  made  of  these  results  with 
those  previously  obtained  with  high  currents. 

The  conditions  of  work  were  as  follows.  The  current  was 
kept  in  almost  all  cases  below  one  ampere.  Currents  below  0.3 
or  0.4  ampere  were  not  found  useful.  The  rotating  dish  anode 
used  first  by  Miss  Langness  (Thesis,  1906)  was  employed.  The 
cathode  was  a  platinum  dish  of  200  c.  c.  capacity,  the  usual  form 
of  dish  used  in  electro-analysis.  The  time  required  for  a  de- 
termination was  about  forty-five  minutes,  or  one  hour,  and  the 
electrolytes  used  were  (i)  sulphuric  acid,  and  (2)  ammonium 
acetate  and  acetic  acid. 


EXPERIMENTAL  PART. , 

A.     SULPHURIC  ACID  ELECTROLYTE. 

I.  Precipitation  of  cadmium  alone.  A  solution  of  cadmium 
sulphate  was  used,  containing  about  0.2  g.  of  cadmium  metal 
in  10  c.  c.  The  first  problem  was  the  determination  of  the  low- 
est possible  current  at  which  the  cadmium  could  be  completely 
precipitated.  Varying  quantities  of  sulphuric  acid  were  tried, 
the  best  results  being  obtained  with  i  c.  c.  or  0.5  c.  c.  of  acid  of 
specific  gravity  1.09.  The  solution  was  not  heated  before  elec- 
trolysis. Ten  c.  c.  of  cadmium  sulphate  were 'placed  in  the  plati- 
num dish,  the  desired  amount  of  sulphuric  acid  added,  the  solu- 
tion diluted  to  60  c.  c.,  and  then  electrolyzed  at  room  tempera- 
ture. The  volume  of  solution  should  not  exceed  60-65  c-  c- 
when  the  dish  anode  is  used,  in  order  that  splashing  may  be 
avoided.  A  speed  of  300-400  revolutions  a  minute  gave  the 
best  results.  The  deposits  were  smooth  and  adherent,  with  fine 
crystals  in  the  center  of  the  dish.  It  was  found  that  washing 
with  hot  water  tended  to  loosen  these  crystals,  and  loss  was 
thereby  incurred.  Cold  water  was  therefore  used  for  washing, 
except  in  special  cases. 


Results  of  this  work  were  as  follows : 


CdSO* 
Cd 

in  grams 
0.2070 
0.2070 
0.2070 
0.2070 
0.2070 
0.2070 
0.2070 


H2S04 

sp.  gr.  1.09 

c.  c. 


N.  D.10 
Amperes    Volts        Time 


Error  in 
Cd  found  grams 


o.i  2.5  4hr.  lomin.  0.1959  — o.om 

0.2  2.75  45  min.  0.1625  —0.0445 

0.3  2.75  i  hr.  20  min.  0.2068  —0.0002 

O-3  2.75-3  i  nr-  IS  min.  0.2067  — 0.0003 

0.3  2.75  45  min.  0.2063  — 0.0007 

0.3  2.75  45  min.  0.2069  — o.oooi 

0.3-0.4          3  45  min.  0.2074  -{-0.0004 


It  was  therefore  concluded  that  with  a  current  of  0.3  ampere, 
complete  precipitation  of  the  cadmium  could  be  obtained  in  forty- 
five  minutes.  An  effort  to  decrease  the  time  did  not  appear  suc- 
cessful. In  many  of  the  following  separations,  the  current  was 
held  at  0.4  ampere,  sometimes  raising  it  to  0.5  for  the  last  ten 
or  fifteen  minutes. 

II.     Separation  of  cadmium  from  metals  of  Group  III. 

(a.)   From  aluminium. 

Ten  c.  c.  of  cadmium  sulphate  solution  and  25  c.  c.  of  aluminium 
sulphate  solution  (0.181 1  g.  aluminium  in  25  c.  c.)  were  placed 
in  the  platinum  dish,  i  c.  c.  sulphuric  acid  (sp.  gr.  1.09)  added, 
and  the  electrolysis  conducted  at  room  temperature. 


CdSO«      A12(SO4)3   H2SO4  N.D.MO 

Cd 

Al     sp. 

gr. 

1.09 

in  grams 

in  grams 

c.c 

Amperes 

Volts 

Time 

i.  0.2051 

0.1811 

i 

0.4 

3 

45  min. 

2.  0.2051 

0.1811 

I 

0.4 

2.75 

45  min. 

3-  0.2051 

0.1811 

i 

0.4 

275 

45  min. 

4.  0.2051 

0.1811 

I 

0.4-0.5 

2-75 

45  min. 

5.  0.2051 

0.181  1 

i 

0.4-0.5 

2.75 

45  min. 

6.  0.2051 

0.181  1 

i 

0.4-0.5 

2.75 

45  min. 

Error  in 
3d  found  grams 
0.2052  -fo.oooi 
0.2051  o.oooo 
0.2054  +0.0003 
0.2047  — 0.0004 
0.2047  — 0.0004 
0.2051  o.oooo 


Similar  results  were  obtained  by  Ashbrook,  using  high  cur- 
rents. 


(b.)   From  chromium. 

The, experiments  with  chromium  were  not  so  conclusive.  The 
amount  of  cadmium  deposited  at  0.4  ampere  was  uncertain,  gen- 
erally low  in  weight.  With  a  current  of  0.7  ampere,  the  de- 
posits were  too  high  in  weight,  but  after  treating  them  with  hot 
water,  the  weight  became  less,  in  some  cases  reaching  the  theo- 
retical amount.  The  deposits  were  somewhat  dark  and  irregu- 
lar in  appearance.  They  evidently  occluded  mother  liquor,  for 
on  treating  one  deposit  with  nitric  acid,  and  evaporating  the 
solution  to  dryness,  a  greenish  residue  was  obtained.  No  de- 
cisive test  for  cadmium  was  obtained  from  the  filtrates  of  ex- 
periments 4  and  5.  It  is,  therefore,  probable  that  there  is  really 
a  separation  here,  but  not  entirely  clear-cut. 


CdSO<         Cr2(S04)s  HUSO*  N.  D., 


Cd 

Cr 

so.  gr.  i.  09 

Error  in 

in  grams 

in  grams  c.c  Amperes    Volts 

Time       Cd  found  grams 

I. 

0.2051 

0.2635 

0.5        0.4           2.8 

ihr. 

0.2052 

+0.000  1 

2.. 

0.2051 

0.2635 

0.5        0.4           2.5 

45  min. 

0.1081 

—  0.0970 

3- 

0.2051 

0.2635 

0.5     0.4-0.5      2.5-3 

ihr. 

0.1696 

—0.0355 

4- 

0.2051 

0.2635 

0.5    0.4-0.75        3-4 

ihr. 

0.2065 

after  washing  with 

hot  water 

0.2053 

4-0.0002 

5- 

0.2051 

0.2635 

0.5     0.4-0.55     2.75-3 

ihr. 

0.2065 

after  washing  with 

hot  water 

0.2057 

-j-o.0006 

6. 

0.1936 

0.2763 

0-5        0.7             3  . 

ihr. 

0.1955 

after  washing  with 

hot  water 

0.1952 

+0.0016 

Ashbrook  attempted  to  separate  cadmium  from  chromium, 
using  high  currents,  but  states  that  in  sulphuric  acid  solution, 
the  deposit  always  weighed  low.  With  phosphoric  acid,  how- 
ever, he  obtained  a  successful  separation. 

(c.)   From  iron. 
I.  Ferric  iron. 

A  solution  of  ferric  ammonium  sulphate  was  used,  contain- 
ing 0.2554  g.  of  iron  in  25  c.  c.  On  electrolyzing  25  c.  c.  of  this 
solution  at  0.4  ampere  and  1.75  volts  for  forty-five  minutes,  no 
deposit  was  obtained.  From  a  mixture  of  10  c.  c.  of  the 
solution  of  cadmium  sulphate  with  ferric  ammonium  sulphate 
(25  c.  c.),  only  a  slight  deposit  of  cadmium  was  obtained 
at  0.4  ampere.  A  current  of  0.8  ampere  was  then  tried  with 
the  iron  solution,  and  no  deposit  obtained.  Electrolyzing  a  mix- 
ture of  the  cadmium  and  iron  solutions  with  a  current  of  0.8- 
0.9  ampere,  deposits  of  cadmium  were  obtained,  but  they  were 
not  of  theoretical  weight.  In  one  case  (exp.  2,  given  below), 
a  little  dilute  sodium  hydroxide  solution  was  added  during  the 
electrolysis.  The  filtrate  from  this  experiment  showed  no  test 
for  cadmium,  but  the  deposit  was  contaminated  with  iron.  In 
experiments  3  and  4,  not  only  was  iron  found  in  the  deposit,  but 
cadmium  was  present  in  the  filtrate. 

Fe2(S04)3 
(NH4)2SO4  H2SO4 

CdSO*    24H2O    sp.  gr.  1.09  N.  D.10o 

Cd  Fe 

in  grms    in  grams  c.c  Amp. 

1.  0.2050    0.2554          i  0.8 

2.  0.2050    0.2554          i  0.8 

(3  c.c.  NaOH) 

3.  0.2050    0.2554          i  0.8-0.9      2.5-3.5 

4.  0.2050    0.2554          i  0.8-0.9         3-4 


Metal  Test    Test 

Volts        Time        found  dep't  filtrate 
2.75-3  ihr.  30  min.  0.1893 

3      i  hr.  30  min.  0.2182     Fe    No  Cd 


45  min.  0.2058    Fe 
45  min.  0.2070    Fe 


Cd 
Cd 


Therefore,  no  satisfactory  separation  of  cadmium  from  ferric 
iron  was  obtained  under  these  conditions.  The  iron  tends  both 
to  hold  back  the  cadmium,  and  to  be  partially  precipitated  with 
that  metal. 

2.  Ferrous  iron. 

The  attempt  was  next  made  to  separate  cadmium  from  fer- 
rous iron.  To  10  c.  c.  of  the  cadmium  sulphate  solution,  acidu- 
lated with  sulphuric  acid  as  before,  I  gram  of  ferrous  sulphate 
was  added,  the  solution  diluted  to  60  c.  c.,  and  electrolyzed. 
In  the  first  trial  a  satisfactory  result  was  obtained.  The  deposit 
weighed  0.2053  g.  (cadmium  taken,  0.2050  g.),  and  showed  no 
test  for  iron.  Further,  the  filtrate  gave  no  test  for  cadmium. 
Subsequent  trials,  however,  gave  low  results,  but  the  deposits 
were  always  free  from  iron.  The  higher  the  current,  the  less 
metal  was  deposited. 

Attempts  were  made  to  introduce  reducing  agents  into  the 
electrolyte,  endeavoring  to  keep  the  iron  in  the  ferrous  condi- 
tion, as  it  was  considered  that  the  incomplete  precipitation  of 
cadmium  might  be  due  to  the  presence  of  ferric  iron  formed 
by  the  oxidizing  action  of  the  current.  Potassium  cyanide  was 
tried,  also  sulphurous  acid,  and  finally,  a  higher  current  was 
employed.  In  the  last  case,  the  cadmium  was  thoroughly  pre- 
cipitated, but  the  deposit  was  contaminated  with  iron. 

CdSO<  FeSO*  H2S04  N.  D™ 

Cd  Fe  sp.  gr.  1.09  Metal      Test        Test 

in  grams  in  grams      c.c  Amp.  Volts  Time    found     deposit    filtrate 

1.  0.2050  0.2-j-          i  3.5  45  min.  0.2053    No  Fe     No  Cd 

2.  0.2050  o.2-[-          i  0.8-0.85  3-3.25  45  min.  0.2012     No  Fe           Cd 

3.  0.2050  0.2-j-          i  0.8-0.9       3  45  min.  0.1891     No  Fe 

4.  0.2050  0.2-j-          i  i.o       3  45  min.  0.1737 

5.  0.2050  0.2-j-          i  0.75-0.8  1.5-2.5  45  min.  0.1995 

i  g.  KCN 

6  0.2050    0.2-f-          i  0.8         2.5  45  mini  0.1581 

3  drops  H2SO3 

7  0.2050    o.2-f          i  0.4-0.6-1.8  1.5-3.5  45  min.  0.2065    Fe          No  Cd 

3  drops  H2SO3 

It  is  evident,  therefore,  that  with  low  currents,  the  separa- 
tion of  cadmium  from  iron  is  not  a  success.  An  entirely  suc- 
cessful separation  of  these  two  metals  was  obtained  by  Miss 
Davison  (Thesis,  1905)  in  twenty  or  twenty-five  minutes,  using 
a  potassium  cyanide  electrolyte  and  a  current  of  five  amperes. 


8 

With  the  same  current,  Ashbrook  found  the  separation  possible 
in  ten  minutes,  both  in  sulphuric  acid  and  phosphoric  acid  solu- 
tion. 

III.     Separation  of  cadmium  from  metals  of  Group  IV. 
(a.)   From  cobalt. 

No  deposit  of  cobalt  was  obtained  by  electrolyzing  a  solution 
containing  0.1808  g.  of  cobalt  at  0.4  ampere  and  2.5  volts  for 
one  hour  and  twenty-five  minutes.  Satisfactory  separations  of 
cadmium  from  cobalt  were  then  made,  as  shown  by  the  following 
data : 


CdSO4 

CoSO4  H2SO4  N.  D.MO 

Cd 

Co    sp.  gr.  1.09 

Error  in 

in  grams 

in  grams 

c.c.  Amperes    Volts 

Time 

Cd  found  grams 

i.  0.2051 
2.  0.2051 
3-  0.2051 
4.  0.2051 

o.i  808 
o.i  808 
0.1808 
o.i  808 

I          0.4           2.5 
i      0.4-0.5     2.5-2.75 
i      0.4-0.5       2.5-3 
i      0.4-0.5      2.5-2.9 

45  min. 
45  min. 
45  min. 
45  min. 

0.2048    —  0.0003 
0.2051        o.oooo 
0.2055     +0.0004 
0.2045    —  0.0006 

In  contrast  to  the  results  under  iron,  the  use  of  a  low  cur- 
rent makes  possible  a  separation  of  cadmium  from  cobalt  which 
is  not  obtained  with  high  currents.  Ashbrook  tried  this 
separation,  but  found  that  in  both  sulphuric  acid  and  phos- 
phoric acid  solution,  cobalt  was  partially  precipitated.  Miss 
Davison  tried  the  separation  of  cadmium  from  cobalt  in 
cyanide  solution,  but  found  that  the  precipitation  was  not 
complete,'  even  after  thirty-five  minutes.  Here,  even  with 
the  low  current  of  0.4  ampere,  the  precipitation  is  com- 
plete in  forty-five  minutes.  With  stationary  electrodes,  the  sepa- 
ration of  cadmium  takes  place  using  a  still  lower  current,  0.078 
ampere,  but  four  to  four  and  a  half  hours  are  required. 

(b.)   From  nickel. 

It  was  found  difficult  to  make  a  clean  separation  of  cadmium 
from  nickel.  On  first  trial,  no  deposit  was  observed  from  10 
c.  c.  of  nickel  sulphate  solution  containing  0.1630  grams  of 
nickel,  electrolyzed  at  0.3  ampere  for  forty-five  minutes,  using 
i  c.  c.  of  sulphuric  acid,  sp.  gr.  1.09,  as  electrolyte.  Separations 
of  cadmium  from  nickel  were  then  tried  as  follows : 


Error  in 

Volts 

Time 

Cd  found  grams 

2-5+ 

45  min. 

0.2067    —  0.0003 

3.25 

45  min. 

0.2073     +0.0003 

2.75 

45  min. 

0.2074    +0.0004 

CdSO4  NiSCX  H2SO4  N.  D.10o 

Cd  Ni     sp.  gr.  1.09 

in  grams  in  grams       c.c.  Amperes 

1.  0.2070  0.1630          I          0.3 

2.  0.2070  0.1630          i          0.3 

3.  0.2070  0.1630         I          0.3 

These  separations  seemed  satisfactory,  but  on  raising  the 
current  to  0.4  ampere,  deposits  too  high  in  weight  were  obtained. 

4.  0.2070     0.1630    I    0.4      3     45  min.    0.2083  -{-0.0013 

5.  0.2070     0.1630    i    0.4     3    45  min.   0.2091  -{-0.0021 

.  Nickel  sulphate  solution  was  then  tried  alone,  both  at  0.4  and 
0.3  ampere. 

6.  0.2053   0.5    0.4     2.5   i  hr.  15  min.  0.0028 

7.  0.2053   0.5    0.3     2.3    50  min.    0.0013 

These  deposits  were  shown  to  be  nickel,  since  they  gave  a 
green  solution  with  nitric  acid.  On  evaporating  to  dryness,  a 
black  residue  was  obtained  which  dissolved  in  nitric  acid  to  a 
green  solution.  The  weight  of  these  deposits  corresponded  closely 
to  the  error  in  weight  of  the  metal  in  experiments  4  and  5.  A 
series  of  determinations  was  then  made,  varying  the  strength  of 
the  current  from  0.3  to  0.5  ampere,  and  the  time  of  electrolysis 
from  forty-five  minutes  to  an  hour  and  a  half.  In  each  case 
the  deposit  was  tested  for  nickel  with  potassium  sulphocarbon- 
ate  and  a  pinkish  color  obtained,  except  in  experiment  9.  The 
filtrates  seemed  free  from  cadmium. 

Test     Error  in 
deposit    grams 

Ni      +  0.0027 
No  Ni      +0.0008 
2068  Trace  Ni  +0.0018 
Ni      +0.0010 
Ni      +0.0021 
Ni      +0.0010 
Ni      +0.0019 
Ni      +  0.0020 
.1941  Trace  Ni  +0.0005 

The  best  results  appear  to  have  been  obtained  in  experiments 
1-3,  using  0.3  ampere  for  forty-five  minutes.  Increasing  the 
current,  or  the  time,  seems  to  increase  the  amount  of  nickel  in 
the  deposit.  The  deposits  in  1-3  were,  unfortunately,  not  tested 
for  nickel.  The  conclusions  drawn  from  them,  however,  were 
confirmed  by  experiment  16,  where  a  current  of  0.3  ampere  was 
applied  for  forty-five  minutes.  The  deposit  showed  but  a  trace 
of  nickel,  and  the  error  in  weight  was  only  0.0005  gram. 

Miss  Davison,  working  with  the  cyanide  electrolyte,  always 


CdSO* 

NiSO4 

H2S04 

N.D.joo 

Cd 

Ni 

sp.  gr.  1.09 

Metal 

in   grams 

in  grams 

c.  c. 

Amperes 

Volts         Time         found 

8. 

0.2050 

0.2053 

0.5 

0.4 

2.8 

hr.  5  min     0.2077 

0. 

0.205.0 

0.2053 

0.5 

0.3 

2.5 

hr.                  0.2058 

to. 

0.2050 

0.2053 

0.5 

0.3 

2.5 

o  min. 

2068 

r  i. 

0.2050 

0.2053 

0.5 

0.3 

2.5 

hr.  5  min. 

.2060 

T  2. 

0.2050 

0.2053 

0.5 

0-3 

2.5 

hr.  5  min. 

.2071 

13- 

0.1936 

0.2053 

0.5 

0.4-0.5 

hr.  10  min. 

.1946 

14- 

0.1936 

0.2053 

0.5 

0.3 

2-75 

hr.  30  min. 

•  1955 

15- 

0.1936 

0.2053 

0.5 

0.3 

2-5 

hr. 

.1956 

16. 

0.1936 

0.2053 

o-5 

0.3 

2.7     45  min. 

.1941 

10 

found  some  nickel  in  the  cadmium  deposit.  Ashbrook  had  the 
same  experience  when  using  phosphoric  acid  solution,  but  ob- 
tained a  satisfactory  separation  with  sulphuric  acid  as  electrolyte, 
using  a  current  of  5  amperes. 

(c.)   From  manganese. 

It  was  found  that  manganese  itself  is  precipitated  under  the 
conditions  used  for  cadmium.  The  deposit  of  manganese  diox- 
ide on  the  dish  anode  was  not  adherent,  and  fell  in  flakes  upon 
the  cathode,  tending  to  contaminate  the  cadmium  deposit.  By 
reversing  the  poles,  making  the  stationary  dish  the  anode,  and 
the  rotating  dish  the  cathode,  a  clean  deposit  of  cadmium  was 
obtained.  The  manganese  dioxide,  though  not  adherent,  was 
retained  upon  the  lower  dish.  There  is  a  distinct  advantage  in 
this  form  of  electrode,  since  it  can  be  used  as  a  cathode  as  well 
as  an  anode,  having  sufficient  surface  to  retain  firmly  a  deposit 
of  0.2  gram  of  metal. 

A  small  amount  of  the  cadmium  sulphate  solution,  5  c.  c., 
(0.10255  g.  cadmium),  was  first  tried,  and  then  the  usual  volume 
of  10  c.  c.  In  all  cases,  manganese  was  found  in  the  filtrates. 
Under  these  conditions,  then,  manganese  is  only  partially  pre- 
cipitated, hence  no  quantitative  separation  of  it  could  be  made. 
Varying  quantities  of  manganese  were  used  in  these  experiments, 
but  always  with  the  result  that  the  cadmium  deposit  was  low  in 
weight  when  as  much  as  0.2  g.  of  cadmium  was  employed. 


CdSO. 

MnSO»      H2SCX 

N.  D.«o 

Cd 

Mn      Sp.  gr.  1.09 

Cd 

Error  in 

in  grams 

in  grams        c.c.      Amperes 

Volts 

Time 

found 

grams 

I 

.  0.10255 

0.2421 

0.4-0.5 

3-3-25 

30  min. 

O.IO20 

—  0.0005 

2.   O.205I 

0.0484 

0.4-0.5 

2.5-2.8 

45  min. 

0.2032 

—  0.0019 

3 

0.2051 

0.0484 

0.4-0.5 

2.5 

45  min. 

O.2O22 

—0.0029 

4 

0.2051 

0.0484 

0.4-0.5 

2.7-3  i 

hr.  15  min. 

0.202Q 

—  0.0022 

5 

0.2051 

0.0484 

0.4-0.5-0.6 

2.5-3 

45  min. 

O.2022 

—  0.0029 

6 

0.2051 

0.2421 

0.4-0.5 

2-5+ 

45  min. 

0.2031 

—  0.0020 

7 

.  0.2051 

0.2421 

0.4-0.5 

2.75+ 

45  min. 

0.2O2I 

—  0.0030 

2  drops  NH4OH 

High  currents  are  evidently  best  for  this  separation,  since 
Ashbrook  separated  cadmium  completely  from  manganese,  both 
in  sulphuric  acid  and  phosphoric  acid  solution,  using  a  current  of 
five  amperes. 

The  possibility  of  formic  acid  as  an  electrolyte  for  this  sepa- 
ration was  then  considered,  as  formic  acid  is  one  of  the  best 
electrolytes  for  cadmium  and  for  manganese  when  determined 


11 


singly.     It  proved  to  be  successful.     The  deposits  of  cadmium 
obtained  were  especially  beautiful,  soft  and  velvety  in  appear- 
ance, and  of  changing  shades  of  silver  gray. 
CdSO4    MnSO«    Formic       N.  D.100 

Cd          Mn  Acid  Cd 

c.c.       Amperes    Volts        Time        found 
5  0.4-0.5      2.5-3  i  hr.        0.2054 

5  0.4  2.5  i  hr.        0.2058 

5  0.4  2.5      i  hr.  25  min.    0.2051 

5  0.4  2.75  45  min.     0.2045 


in  grams  in  grams 

1.  0.2051  0.2421 

2.  0.2051  0.2421 

3.  0.2051  0.2421 

4.  0.2051  0.2421 


Error  in 
grams 
+0.0003 
-[-0.0007 
o.oooo 
— 0.0006 


(d.)   From  zinc. 


A  satisfactory  separation  of  cadmium  from  zinc  was  obtained. 
No  deposit  of  zinc  appeared  from  the  electrolysis  of  10  c.  c. 
of  zinc  sulphate  solution  containing  0.2094  grams  of  zinc,  using 
a  current  of  0.4  ampere  for  forty-five  minutes.  Separations  of 
cadmium  from  zinc  were  then  tried  under  the  same  conditions. 
The  deposits  were  dissolved  in  nitric  acid  and  tested  for  zinc 
on  charcoal  with  the  blowpipe,  fusing  with  sodium  carbonate  and 
moistening  with  cobalt  nitrate.  No  test  for  zinc  was  obtained, 
and  the  filtrates  were  free  from  cadmium. 

CdSO4    ZnSO4      H2SO4       N.  D.ioo 

Cd          Zn      Sp.  gr.  1.09 
in  grams  in  grams       c.c.       Amperes    Volts 


Cd 

found 


I.  0.2050 

O.20Q4 

0.4 

2.75-2.9 

2.  O.2050 

0.2094 

0.4 

3 

3.  0.2050 

0.2094 

0.4 

2-75 

4.  0.2050 

0.2O94 

0.4 

2-75 

5.  0.2050 

0.2094 

0.4 

3 

Error  in 
grams 
+0.0003 
+0.0007 
+0.0007 
o.oooo 
— 0.0002 


Time 

45  min.  0.2053 

45  min.  0.2057 

45  min.  0.2057 

45  min.  0.2050 

45  min.  0.2048 

Ashbrook  reports  that  "zinc  always  came  down  with  the  cad- 
mium in  sulphuric  acid  solution,  and  also  in  phosphoric  acid 
solution."  Here,  then,  is  another  case  like  the  cadmium  cobalt 
separation,  in  which  a  low  current  is  successful  where  a  high 
current  has  failed.  Here,  again,  the  separation  may  be  obtained 
with  stationary  electrodes,  and  has  been  worked  out  with  various 
electrolytes,  but  the  time  required  is  from  three  to  ten  hours. 

IV.  Separation  of  cadmium  from  magnesium.  The  experi- 
ments on  these  two  metals  also  resulted  in  a  satisfactory  sepa- 
ration. 

CdSO4  MgSO4      H2SO4       N.D.IOO 

Cd  Mg      Sp.gr.  1.09                                                       Cd  Error  in 

in  grams  in  grams       c.c        Amperes  Volts        Time  found  grams 

1.  0.2051  0.1785          0.5       0.4-0.5  3          45  min.  0.2055  +0.0004 

2.  0.2051  0.1785          0.5      0.4-0.5-0.6  3          50  min.  0.2053  +0.0002 
3.0.2051  0.1785          0.5      0.4  2.7 1  hr.  5  min.  0.2051  o.oooo 


12 
Similar  results  were  obtained  by  Ashbrook  with  magnesium, 

using  high  currents. 

B.     ACETATE  ELECTROLYTE. 

The  electrolyte  used  in  these  determinations  was  i  gram  of 
ammonium  acetate  together  with  0.5  c.  c.,  or  more  often  i  c.  c., 
of  acetic  acid,  1:3  by  volume  ( i  volume  glacial  acetic  acid  to 
3  of  water).  The  solutions  were  heated  just  below  boiling 
before  electrolyzing.  This  preliminary  heating  was  found  to  be 
quite  necessary,  influencing  the  character  of  the  deposit  to  a 
considerable  extent.  The  deposits  of  cadmium  from  the  acetate 
electrolyte  are  more  coarsely  crystalline  than  from  the  sulphuric 
acid  electrolyte,  and  hence  sometimes  not  adherent.  If  proper 
care  is  exercised,  however,  there  need  be  no  loss  of  metal.  Cold 
water  was  used  in  washing  the  deposits,  as  in  the  other  set  of 
determinations. 


I.     Precipitation  of  cadmium  alone. 

CdS04    ig.  NH4C2H302    N.D.M. 
C2H402(i:3) 


Cd 


in  grams 
I.  0.2051 
2..  0.2051 

3.  0.2051 

4.  0.2051 

5.  0.2051 

6.  0.2051 

7.  0.2051 

8.  0.2051 


c.c. 

0-5 
0-5 
0.5 


Amperes 

Volts        Time 

0.05 

2.25           20  min. 

O.I 

2.5             25  min. 

0.15 

2.7  i  hr. 

0.2 

2.5  2  hrs.  30  min. 

0.2 

2.5  ihr.  5  rrtin. 

0.05-0.3 

2.3-3  ihr. 

0.3 

3      ihr. 

0.3 

2.75  ihr. 

— 0.00 1 1 

+0.0003 

— O.OOIO 
0.0000 

—0.0003 

-j-O.OOOI 


Cd        Error  in 
found      grams 
No  deposit 
Trace  of  deposit 
0.2040 
0.2054 
0.2041 
0.2051 
0.2048 
0.2052 

0.3  ampere  was,  therefore,  taken  as  the  current  to  be  used  for 
further  work.  The  time  can  be  reduced  to  forty-five  minutes. 

II.     Separation  of  cadmium  from  metals  of  Group  III. 
(a.)   From  aluminium. 

It  was  in  the  course  of  the  work  on  these  separations  that  the 
necessity  of  heating  the  solutions  before  electrolysis  was  made 
evident.  Several  separations  of  cadmium  from  aluminium,  and 
several  determinations  of  cadmium  alone,  were  'tried  at  ordinary 
temperature.  The  weight  of  metal  was  invariably  high,  the 
deposit  containing  coarse  crystals,  and  having  a  tendency  to 
sponginess,  and  hence  occluding  mother  liquor.  On  heating  the 
solutions,  however,  the  deposits  were  adherent,  and  not  spongy, 
and  the  weights  were  more  satisfactory.  The  difference  in  de- 
posits from  cold  and  hot  solutions  is  shown  as  follows: 


CdSO4 
Cd 
in  grams 
I.  0.1936 
2.  0.1936 
3-  0.1936 
4-  0.1936 
5-  0.19^6 

ig.  NH4C2H3Oa 
C2H4O2(i:3) 
c.c 
I 
I 
I 
I 

I 

13 

COLD 
N.D.XOO 

Amperes    Volts 
0.3            2.8 
0-3             3- 
0.3             2.9 
0.3             2.8 
0.3             3- 

Time 
ihr. 
50  min. 
45  niin. 
45  min. 
45 


found 
0.2000 
0.1940 
0.1936 
0.1951 
0.1941 


Error  in 
grams 
+0.0064 
-J-O.OOO4 
o.oooo 
+0.0015 
+0.0005 


In  experiment  3,  the  deposit  was  washed  with  hot  water  be- 
fore weighing. 

HOT 


6.  0.1936 

I 

0-3 

3 

45  min.          0.1938    +0.0002 

7-  0.1936 

I 

0-3 

2-5 

45  min.           0.1936        o.oooo 

CdSO4 

A12(S04)3 

ig.  NH4C2H3O2 

COLD 

Cd 

Al 

in  grams 

in  grams 

CoH4O2(i: 

3)       N.  D.100 

Cd      Error  in 

c.c. 

Amperes 

Volts       Time       found     grams. 

i.      0.1936 

0.1811 

i 

0.3 

2.7-3.2     45  min.   0.1964     +0.0028 

2.     0.1936 

O.22OO 

i 

0.3 

2.7            45  min.   0.1958     +0.0022 

HOT 

3-     0.1936 

0.2200 

i 

0.3 

2.75          45  min.   0.1934    —  0.0002 

4-      0.1936 

O.22OO 

i 

0-3 

3               45  min.   0.1941      +0.0005 

5-      0.1936 

O.2200 

i 

0-3 

2.5            45  min.   0.1946     +0.0011 

6.     0.1936 

0.22OO 

i 

0-3 

2.75          45  min.  0.1932    —  0.0004 

Experiment  5  shows  that  high  results  may  be  obtained  even 
when  the  solution  is  heated  before  electrolysis. 

(b.)   From  chromium. 

No  satisfactory  separation  of  cadmium  from  chromium  was 
obtained,  but  some  very  curious  deposits  attracted  attention. 
Ammonium  acetate  alone,  and  acetic  acid  alone,  were  tried  as 
electrolytes,  as  well  as  the  combination  of  the  two.  The  cur- 
rent was  varied  from  0.3  to  0.9  ampere.  The  chromium  solu- 
tion used  was  the  green  sulphate.  When  ammonium  acetate 
together  with  acetic  acid,  or  ammonium  acetate  alone,  was  used, 
the  solution  became  yellow  in  color,  showing  oxidation.  When, 
however,  acetic  acid  was  used  alone,  the  color  remained  green. 
No  different  results  were  obtained  from  these  changes  in  the 
electrolyte.  The  deposits  were  peculiar  in  form;  the  metal  was 
deposited  in  ridges,  radiating  from  a  dark  gray  center,  most  of 
the  metal  being  bright  and  silvery  in  appearance.  There  was 
considerable  green  color  in  the  deposits,  suggesting  occlusion  of 
chromium  salts.  Repeated  washings  with  hot  water  lowered  the 
weight  of  the  precipitate,  but  did  not  remove  the  green  color  to 
any  great  extent.  A  deposit  weighing  0.2274  g.,  after  being 
washed  with  hot  water,  weighed  successively  0.2124  g.,  0.2114  g., 


14 

and  0.2098  g.  The  deposit  was  still  green  in  color.  The  cad- 
mium taken  was  0.2051  g.  Cadmium  was  sometimes  found  in 
the  filtrate,  so  that  the  weight  of  the  deposits  did  not  necessarily 
indicate  complete  precipitation  of  the  cadmium.  The  washings 
were  sometimes  colorless,  and .  sometimes  green  in  color,  but  in 
both  cases  gave  tests  for  a  sulphate  with  barium  chloride  and 
hydrochloric  acid.  The  deposits  dissolved  instantly  in  nitric  acid 
to  a  green  solution  which,  with  ammonium  hydroxide,  gave  a 
gray-green  precipitate,  showing  the  presence  of  chromium  in 
some  form. 

(c.)   From  iron. 

1.  Ferric  iron. 

As  in  the  case  of  chromium,  no  satisfactory  results  were  ob- 
tained. The  same  variation  in  the  electrolyte  was  employed  as 
under  chromium,  ammonium  acetate  alone,  acetic  acid  alone,  and 
the  combination  of  the  two.  The  current  was  varied  from  0.3 
to  0.9  ampere.  The  deposits  were  spongy  and  dark,  with  traces 
of  basic  salt.  They  had  the  appearance  of  containing  iron,  and 
always  gave  evidence  of  that  metal  by  the  sulphocyanate  test. 

2.  Ferrous  iron. 

One  gram  of  ferrous  sulphate  was  used,  and  the  customary 
amount  of  ammonium  acetate  and  acetic  acid.  In  two  experi- 
ments, using  0.3  ampere  for  forty-five  minutes,  the  following 
results  were  obtained: 

Cd  present  Cd  found  Error  in  grams 

0.1936  0.1980  +0.0044 

0.1936  0.1819  — 0.0117 

One  deposit  was  high,  the  other  low  in  weight,  but  both  had 
the  appearance  of  containing  iron,  and  both  gave  tests  for  that 
metal. 

III.     Separation  of  cadmium  from  metals  of  Group  IV. 
(a.)   From  cobalt. 

When  a  solution  of  cobalt  sulphate  (0.1808  g.  cobalt)  was 
subjected  to  electrolysis  at  0.3  ampere  with  the  acetate  electro- 
lyte (i  g.  ammonium  acetate  and  I  c.  c.  acetic  acid  1:3),  the 
solution  turned  brown,  indicating  oxidation,  and  there  was  a 
slight  metallic  deposit  on  the  cathode  and  also  on  the  anode. 
These  deposits  dissolved  in  nitric  acid,  the  heavier  cathode  de- 
posit giving  a  pink  solution,  the  anode  deposit  a  colorless  solu- 


15 


Co 

found 
0.0176 
0.0339 


tion.  Sodium  hydroxide,  however,  gave  a  dark  precipitate  with 
this  colorless  solution,  and  on  testing  this  precipitate  with  a 
borax  bead,  a  blue  color  was  obtained.  Hence  both  deposits 
were  evidently  cobalt. 

CoSO*  ig.  NH.GH.O,  N.D.M. 

Co  GH408(i:3) 

in  grams  c.c.  Amperes          Volts                Time 

1.  0.1808  i  0.3               2-2.25                i  hr 

2.  0.1808  i  0.3               2.5-3                 i  hr. 

Therefore,  no  separation  of  cadmium   from   cobalt  could  be 
expected  under  these  conditions, 
(b.)   From  nickel. 

Similar  results  were  obtained  with  nickel. 
NiSO4     ig.  NH4GHsO2      N.D.100 

Ni       GH4O2(i:3) 

in  grams          c.c.  Amperes  Volts  Time 

0.2053  i  0.3  2+  i  hr. 

Treatment  of  the  deposit  with  nitric  acid  gave  a  green  solu- 
tion which  turned  blue  when  made  ammoniacal. 

(c.)   From  manganese. 

The  rotating  dish  cathode  was  again  employed,  but  the  weight 
of  the  metal  was  always  low.  The  deposits  were  adherent,  and 
finely  crystallized,  but  had  none  of  the  velvet-like  appearance 
given  by  the  formic  acid  electrolyte. 

CooO4               MnSO4  ig.  NH4C2H3O2    N.  D.ioo 

Cd                 »Mn  C2H402(i:3) 

in  grams           in  grams  c.c.              Amperes     Volts        Time 

0.2421  i                     0.3          1.5-2.5 

0.2421  i                    0.3      1.5-2.5-3.2 


Ni 

found 
0.0392 


i.    0.1936 

2.        0.1936 

3-      0.1936 


0.2421 


0-3 


i-S-3 


45  mm. 
45  niin. 
i  hr. 


Cd      Error  in 
found     grams 
0.1907    — 0.0029 
0.1893    — 0.0043 
0,1869    — 0.0067 


(d.)   From  zinc. 

As  in  the  case  of  cobalt  and  nickel,  zinc  begins  to  be  deposited 
at  such  low  currents  with  an  acetate  electrolyte  that  no  separation 
of  cadmium  from  zinc  is  possible  at  0.3  ampere. 
ZnSCX         NaC2H3O2        N.  D.100 

Zn          GH4Oa(i:3) 
in  grams  Amperes        Volts  Time  Zn  found 

1.  0.2094  0.2  3  30min.  0.0496 

2.  0.2094  0.2  3-2.5  i  hr.  0.0529 

IV.     Separation  of  cadmium  from  magnesium.     This  separa- 
tion was  successful. 


16 

CdSO4  MgSO4        ig.  NH4C2H3O2    N.  D.10o 

Cd  Mg  C2H4O2(i:3)  Cd      Error  in 

in  grams  in  grams  c.c.  Amperes     Volts         Time         found     grams 


1.  0.2051  0.1785 

2.  0.2051  0.1785 

3.  0.2051  0.1785 

4.  0.2051  0.1785 

5.  0.2051  0.1785 


0.3  2.8  i  hr.  0.2049  — 0.0002 

0.3  2.7  i  hr.  0.2054    +0.0003 

°-3  2.5-3  50  min.  0.2050  — o.oooi 

0.3  2.5  55  min.  0.2048  — 0.0003 

°-3  2-S'3-3  45  min.  0.2050  — o.oooi 


The  method  of  testing  the  filtrates  in  this  work  should  be 
mentioned.  The  filtrates  were  evaporated  to  a  small  bulk,  and 
tested  for  cadmium  with  hydrogen  sulphide.  In  the  sulphuric 
acid  solutions,  slight  yellowish-brown  precipitates,  suggesting 
cadmium  sulphide,  were  obtained  in  varying  amounts.  With 
the  acetate  solutions,  no  yellow  precipitates  were  obtained.  A 
clear  yellowish  color  was  sometimes  observed  in  the  solution 
when  the  hydrogen  sulphide  was  first  added,  and  a  grayish 
precipitate  of  sulphur  separated  out  on  further  treatment  with 
the  gas.  In  general,  the  solution  was  perfectly  colorless,  and 
gave  no  evidence  of  cadmium.  Cadmium  deposits  from  the 
same  amount  of  cadmium  sulphate  solution  (10  c.  c.)  weighed 
no  more  from  the  acetate  electrolyte  than  from  the  sulphuric 
acid  electrolyte.  Hence  it  was  concluded  that  if  the  yellowish- 
brown  precipitates  obtained  were  cadmium  sulphide,  only  a  trace 
of  cadmium  was  represented  by  them. 

The  question  arose  as  to  how  much  the  particular  form  of 
anode  used  in  this  work  influenced  the  time  necessary  for  a  de- 
termination. The  dish  anode  should  reduce  the  time  factor 
greatly,  judging  by  its  action  in  previous  work.  To  answer  this 
question  more  definitely,  the  spiral  anode  was  substituted  in  a 
determination  of  cadmium  from  10  c.  c.  of  cadmium  sulphate 
solution,  containing  0.1936  g.  cadmium.  One  c.  c.  sulphuric  acid 
(1.09)  -was  used  as  the  electrolyte,  and  0.4  ampere  as  the  cur- 
rent. After  forty-five  minutes,  the  current  was  interrupted.  The 
deposit  of  cadmium  obtained  weighed  only  0.1742  g.,  proving 
that  complete  precipitation  of  the  metal  by  use  of  the  spiral  anode 
would  require  more  time  than  by  use  of  the  dish  anode. 

CONCLUSION. 

The  object  of  this  investigation,  as  stated  in  the  introduction, 
was  first,  to  prove  whether  satisfactory  separations  of  metals 
could  be  made  with  the  rotating  anode  using  low  currents,  and 
second,  to  throw  some  light  on  the  question  whether  the  rapid 
methods  of  electrolysis  are  of  practical  value  in  conducting  sepa- 
rations. 

The   first   question  is   certainly  answered   in   the  affirmative. 


17 

Separations  of  cadmium  were  made  from  aluminium,  chromium, 
cobalt,  nickel,  zinc,  and  magnesium,  with  the  sulphuric  acid  elec- 
trolyte, from  manganese  with  formic  acid  as  electrolyte,  and 
from  aluminium  and  magnesium  with  the  acetate  electrolyte. 

As  to  the  practical  value  of  the  work,  a  comparison  should 
be  made  of  these  results  with  the  results  obtained  with  stationary 
electrodes,  and  with  the  rotating  anode,  using  high  currents. 
This  comparison  is  best  made  in  tabular  form. 

TABLE  I. 

Sulphuric  Acid  Electrolyte 
Separations  of  Cd  from 


Rotating  Anode 
High  Currents 
Amperes  Time 


Rotating  Anode 

Stationary  Electrodes 

Low  Currents 

Amperes          Time 

Amperes       Time 

Al          .078          4-41/2  hrs. 

0.4              45  min. 

Cr          .078          4-45^  hrs. 

0.4              i  hr. 

Fe          .078          4  4*/2  hrs. 

Not  successful 

Co         .078          4-4l/2  hrs. 

0.4              45  min. 

Ni          .078          4-4^  hrs. 

0.3              45  min. 

Mn        .078         4-4^/2  hrs. 

Not  successful 

Zn         Not  recorded 

0.4             45  min. 

Mg        Not  recorded 

0.4             45  min. 

lomm. 


Not  successful 

Not  successful 
5 

Not  successful 


lomm. 


10  min. 
10  min. 


10  mm. 


TABLE  II. 
Separations  of  Cd  from 


Phosphoric  Acid  Electrolyte 
High  Currents 


Amperes 

Time 

Al 

5 

10  min. 

Cr 

5 

10  min. 

Fe 

5 

10  min. 

Co 

Not  successful 

Ni 

Not  successful 

Mn 

5 

10  min. 

Zn 

Not  successful 

Mg 

5 

10  min. 

Mn 


Acetate  Electrolyte 
Low  Currents 


Amperes 

0-3 

Not  successful 

Not  successful 

Not  successful 

Not  successful 

Not  successful 

Not  successful 


Time 
45  min. 


0-3 


45  mm. 


Formic  Acid  Electrolyte 

Low  Currents 
Amperes  Time 

0.4  i  hr. 


18 

Table  I  shows,  at  once,  the  advantage  of  rotation,  even  with 
low  currents,  over  stationary  electrodes.  A  comparison  of  Tables 
I  and  II  brings  out  the  following  points  in  regard  to  rotation 
with  high  and  with  low  currents: 

1.  Separations  of  cadmium  from  aluminium  and  magnesium 
are  possible  in  all  cases  studied. 

2.  The  best  conditions  for  the  separation  of  cadmium  from 
chromium  are  with  a  high  current  and  phosphoric  acid  as  elec- 
trolyte, although  the  separation  is  possible  with  a  low  current 
in  sulphuric  acid  solution. 

3.  The  separation  of  cadmium  from  iron  is  possible  with  a 
high  current,  but  not  with  a  low  current. 

4.  Separations  of  cadmium  from  cobalt  and  zinc  are  possible 
with  a  low  current,  but  not  with  a  high  current. 

5.  The  separation  of  cadmium  from  nickel  is  possible  with 
both  a  high  and  a  low  current,  but  a  high  current  is  to  be  pre- 
ferred. 

6.  The  separation  of  cadmium  from  manganese  is  best  made 
at  a  high  current,  but  may  be  made  at  a  low  current,  if  formic 
acid  is  the  electrolyte. 

This  study  is,  of  course,  only  a  fragment  of  what  must  be 
done  to  make  clear  the  possibilities  of  electrolytic  separations. 
Work  with  cadmium  should  be  extended,  using  other  metals  and 
other  electrolytes.  Each  metal  in  turn  should  receive  such  a 
complete  treatment.  High  current  separations  need  further  study 
as  well  as  low  current  separations,  as  the  work  already  done 
has  been  confined  to  comparatively  few  metals. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 

THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


20w-l,'22 


YC  21901 


He. 


1 86933 


